Reciprocating piston compressor for refrigerant

ABSTRACT

In order to increase the efficiency, in respect of the quantity of refrigerant to be compressed, of a reciprocating piston compressor for refrigerant, comprising a compressor housing having at least one compressor stage that has at least one cylinder unit, wherein a piston is movably arranged in the cylinder unit, a cylinder drive that is arranged in the compressor housing, for the at least one piston, a valve plate that closes off a cylinder chamber and is provided with at least one suction valve which, for its part, has a suction opening, arranged in the valve plate and closable by a suction vane, and has at least one outlet valve with an outlet opening, wherein the at least one suction valve and the at least one outlet valve are associated with the respective cylinder chamber, and a cylinder head that is arranged on an opposite side of the valve plate to the cylinder chamber, it is proposed that the valve plate should have, on its side facing the cylinder chamber, a recess, which is arranged inside an external contour of an abutment face of the suction vane that is associated with the suction opening and which extends from the suction opening and is open toward this abutment face.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This patent application claims the benefit of German application No. 102022 109 938.5, filed Apr. 25, 2022, the teachings and disclosure ofwhich are hereby incorporated in their entirety by reference thereto.

BACKGROUND OF THE INVENTION

The invention relates to a reciprocating piston compressor forrefrigerant, comprising a compressor housing having at least onecompressor stage that has at least one cylinder unit, which itselfcomprises at least one cylinder chamber, wherein a piston is movablyarranged in the cylinder unit, a cylinder drive that is arranged in thecompressor housing, for the at least one piston, a valve plate thatcloses off the cylinder chamber and is provided with at least onesuction valve which, for its part, has a suction opening, arranged inthe valve plate and closable by a suction vane, and has at least oneoutlet valve with an outlet opening, wherein the at least one suctionvalve and the at least one outlet valve are associated with therespective cylinder chamber, and a cylinder head that is arranged on anopposite side of the valve plate to the cylinder chamber.

Reciprocating piston compressors of this kind are known from the priorart.

There is a need for the efficiency of these to be increased in respectof the quantity of refrigerant to be compressed.

SUMMARY OF THE INVENTION

According to the invention, this object is achieved in the case of areciprocating piston compressor of the type mentioned in theintroduction in that the valve plate has, on its side facing thecylinder chamber, a recess, which is arranged inside an external contourof an abutment face of the suction vane that is associated with thesuction opening and which extends from the suction opening and is opentoward this abutment face.

The advantage of the solution according to the invention can be seen inthe fact that the recess, which adjoins the suction opening and is opentoward the abutment face, provides the possibility of enlarging thesurface area over which the refrigerant to be drawn in by suction actson the suction vane immediately before the suction vane is opened, andin so doing provides the possibility of achieving reliable and quickeropening of the suction vane even at low pressures, and hence betterfilling of the cylinder chamber.

Here, it is particularly favorable if the recess has a recess base thatis set back in relation to the abutment face of the suction vane andthus makes it possible for the refrigerant that is to be drawn in bysuction to be able to flow through the suction opening and into therecess before opening and to be able to act on the suction vane, inorder to open it, in the region of the recess as well, such that alarger surface area of action on the suction vane is available.

Here, favorably the recess base extends into the suction opening, suchthat when the suction vane closes the suction opening the recess cansufficiently quickly fill with refrigerant that is to be drawn in bysuction, and, for the purpose of opening the suction vane, thisrefrigerant can act on the suction vane in addition to the refrigerantthat is in the suction opening.

Furthermore, detailed statements have not yet been made as regards thedepth of the recess.

For example, an advantageous solution provides for the recess, startingfrom the abutment face of the suction vane, to have a depth that isgreater than a thickness of a lubricant film that is formed between thesuction vane and the abutment face when the suction opening is sealedoff.

This solution has the advantage that it makes it possible to prevent therecess from filling with lubricant when the suction vane closes thesuction opening, so that the possibility that refrigerant flows into therecess before the suction vane opens is impeded.

It is particularly favorable if, starting from the abutment face of thesuction vane, the depth of the recess is at least 0.2 mm, in particularat least 0.3 mm.

For example, the depth of the recess is at most 40%, in particular atmost 50%, of the thickness of the valve plate.

A particularly favorable solution provides for the recess to run at aspacing from the external contour of the abutment face of the suctionvane and thus, when the suction opening is closed, for the suction vanealso to sealingly close the recess toward the cylinder chamber.

Moreover, it is preferably provided for the recess and the suctionopening to be surrounded by a contact face for the suction vane thatruns peripherally all the way around them, such that when the suctionopening is closed the recess is sealingly closed with the requiredreliability in order to avoid dead space and to make available asufficiently large contact surface area for the suction vane.

It is particularly favorable in the context of the solution according tothe invention if, on its side facing the suction vane and open towardthe abutment face of the suction vane, the recess has a surface areathat is at least 10%, preferably at least 20%, even more preferably atleast 50% of the cross-sectional surface area of the suction opening.

More detailed statements have not yet been made as regards the course ofthe recess.

In principle, the recess could run around the suction opening, but thiswould be unfavorable from the point of view of the space available.

For this reason, it is preferably provided for the recess to extend fromthe suction opening in the direction of a suction vane foot.

Another advantageous solution provides for the recess to extend from thesuction opening in the direction of a suction vane end.

In order to have enough space for the extent of the recess, it ispreferably provided for the recess to extend from the suction openingover a region of the valve plate that, on the side with the cylinderhead, abuts against a foot region of the cylinder head. As a result, therecess can extend over broad regions of the valve plate even thoughthere is, on the opposite side to the recess, a foot region of thecylinder head that prevents the suction opening itself from beingenlarged.

It is even more advantageous if the recess extends from the suctionopening over a region of the valve plate that delimits an outlet chamberon the side with the cylinder head.

In order to optimize the supply of refrigerant to the suction opening,it is preferably provided for the cylinder head to be provided with aconnector for refrigerant that is to be drawn in.

Preferably here, it is provided for a suction duct to run through thecylinder head from the connector for the refrigerant that is to becompressed as far as the suction opening, and for the duct cross sectionthereof to correspond to at most twice, even more preferably at most 1.5times, a cross-sectional surface area of the suction opening in order toguide the refrigerant that is to be drawn in through the cylinder headas quickly as possible and with as little turbulence as possible andhence to achieve quick, reliable opening of the suction vane even at lowpressures.

Further, it is preferably provided for a suction duct that leads to aplurality of suction openings to have a cross-sectional surface areathat corresponds to at most twice, even more preferably at most 1.5times, the sum of the cross-sectional surface areas of the plurality ofsuction openings.

In one embodiment, the suction duct that runs in the cylinder head isshaped within the cylinder head.

A further embodiment provides for the suction duct to be formed in aninsert that is inserted into the cylinder head.

Moreover, the invention relates to a valve plate for a reciprocatingpiston compressor comprising a compressor housing having at least onecompressor stage that has at least one cylinder unit, which itselfcomprises at least one cylinder chamber, wherein the valve plate closesoff the cylinder chamber and carries a cylinder head and is providedwith at least one suction valve which, for its part, has a suctionopening, arranged in the valve plate and closable by a suction vane, andis provided with at least one outlet valve with an outlet opening,wherein the at least one suction valve and the at least one outlet valveare associated with the respective cylinder chamber.

Preferably, the valve plate takes a form such that it has one or more ofthe features described above.

Thus, the description above of solutions according to the inventioncomprises in particular the different combinations of features that aredefined by the sequentially numbered embodiments below:

1. A reciprocating piston compressor (54) for refrigerant, comprising acompressor housing (130) having at least one compressor stage (112, 142)that has at least one cylinder unit (114, 144), which itself comprisesat least one cylinder chamber (228), wherein a piston (226) is movablyarranged in the cylinder unit (114, 144), a cylinder drive (115, 145)that is arranged in the compressor housing (130), for the at least onepiston (226), a valve plate (232) that closes off the cylinder chamber(228) and is provided with at least one suction valve (240) which, forits part, has a suction opening (242), arranged in the valve plate (232)and closable by a suction vane (246), and has at least one outlet valve(243) with an outlet opening (244), wherein the at least one suctionvalve (240) and the at least one outlet valve (243) are associated withthe respective cylinder chamber (228), and a cylinder head (192, 194)that is arranged on an opposite side of the valve plate (232) to thecylinder chamber (228), wherein the valve plate (232) has, on its sidefacing the cylinder chamber (228), a recess (282), which is arrangedinside an external contour (262) of an abutment face (256) of thesuction vane (246) that is associated with the suction opening (242) andwhich extends from the suction opening (242) and is open toward thisabutment face (256).

2. The reciprocating piston compressor according to embodiment 1,wherein the recess (282) has a recess base (284) that is set back inrelation to the abutment face (256) of the suction vane (246).

3. The reciprocating piston compressor according to embodiment 2,wherein the recess base (284) extends into the suction opening (242).

4. The reciprocating piston compressor according to one of the precedingembodiments, wherein the recess (282), starting from the abutment face(256) of the suction vane (246), has a depth that is greater than athickness of a lubricant film that is formed between the suction vane(246) and the abutment face (256) when the suction opening (242) issealed off.

5. The reciprocating piston compressor according to one of the precedingembodiments, wherein, starting from the abutment face (256) of thesuction vane (246), the depth of the recess (282) is at least 0.2 mm, inparticular at least 0.3 mm.

6. The reciprocating piston compressor according to one of the precedingembodiments, wherein, starting from the abutment face (256) of thesuction vane (246), the depth of the recess (282) is at most 40%, inparticular at most 50%, of the thickness of the valve plate.

7. The reciprocating piston compressor according to one of the precedingembodiments, wherein the recess (282) runs at a spacing from theexternal contour (262) of the abutment face (256) of the suction vane(246).

8. The reciprocating piston compressor according to one of the precedingembodiments, wherein the recess (282) and the suction opening (242) aresurrounded by a contact face (288) for the suction vane (246) that runsperipherally all the way around them.

9. The reciprocating piston compressor according to one of the precedingembodiments, wherein, on its side facing the suction vane (246) and opentoward the abutment face of the suction vane (246), the recess (282) hasa surface area that is at least 10%, preferably at least 20%, even morepreferably at least 50% of a cross-sectional surface area of the suctionopening (242).

10. The reciprocating piston compressor according to one of thepreceding embodiments, wherein the recess (282) extends from the suctionopening (242) in the direction of a suction vane foot (252).

11. The reciprocating piston compressor according to one of thepreceding embodiments, wherein the recess (282) extends from the suctionopening (242) in the direction of a suction vane end (254).

12. The reciprocating piston compressor according to one of thepreceding embodiments, wherein the recess (282) extends from the suctionopening (242) over a region of the valve plate that, on the side withthe cylinder head (192, 194), abuts against a foot region (272, 274) ofthe cylinder head (192, 194).

13. The reciprocating piston compressor according to one of thepreceding embodiments, wherein the recess (282) extends from the suctionopening (242) over a region of the valve plate (292) that delimits anoutlet chamber on the side with the cylinder head (192, 194).

14. The reciprocating piston compressor according to one of thepreceding embodiments, wherein the cylinder head (192, 194) is providedwith a connector (304) for refrigerant that is to be drawn in.

15. The reciprocating piston compressor according to embodiment 14,wherein a suction duct (302, 312, 314) extends through the cylinder head(192, 194) from the connector (304) for the refrigerant that is to becompressed as far as the suction opening (242).

16. The reciprocating piston compressor according to embodiment 15,wherein the suction duct (302, 312, 314) has a duct cross section thatcorresponds to at most twice, even more preferably at most 1.5 times, across-sectional surface area of flow of the suction opening (242).

17. The reciprocating piston compressor according to embodiment 14 to16, wherein a suction duct (312, 314) that leads to a plurality ofsuction openings (242) has a cross-sectional surface area of flow thatcorresponds to at most twice, even more preferably at most 1.5 times,the sum of the cross-sectional surface areas of flow of the suctionducts (312, 314).

18. The reciprocating piston compressor according to one of embodiments15 to 17, wherein the suction duct (302, 312, 314) is shaped within thecylinder head (192′).

19. The reciprocating piston compressor according to one of embodiments15 to 17, wherein the suction duct (302, 312, 314) is formedsubstantially in an insert (316) that is inserted into the cylinder head(192″).

20. A valve plate for a reciprocating piston compressor (54) comprisinga compressor housing (130) having at least one compressor stage (112,142) that has at least one cylinder unit (114, 144), which itselfcomprises at least one cylinder chamber (228), wherein the valve plate(232) closes off the cylinder chamber (228) and carries a cylinder head(192, 194) and is provided with at least one suction valve (240) which,for its part, has a suction opening (242), arranged in the valve plate(232) and closable by a suction vane (246), and is provided with atleast one outlet valve with an outlet opening, wherein the at least onesuction valve (240) and the at least one outlet valve (243) areassociated with the respective cylinder chamber (228), wherein the valveplate (232) has, on its side facing the cylinder chamber (228), a recess(282), which is arranged inside an external contour (262) of an abutmentface (256) of the suction vane (246) that is associated with the suctionopening (242) and which extends from the suction opening (242) and isopen toward this abutment face (256).

21. The valve plate according to embodiment 20, wherein the valve plate(232) has one or more of the features of embodiments 2 to 13.

Further features and advantages of the invention form the subject matterof the description below, and the illustration in the drawing of someexemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic illustration of a refrigeration unit, inparticular taking the form of a transport refrigeration unit, having arefrigeration plant according to the invention;

FIG. 2 shows a schematic illustration of a first exemplary embodiment ofa refrigeration circuit according to the invention, having a pistoncompressor according to the invention;

FIG. 3 shows a cross section in the region of a cylinder chamber of acylinder of a piston compressor according to the invention, providedwith a valve plate and suction valve and a cylinder head;

FIG. 4 shows a plan view, as seen in the direction of the arrow A inFIG. 3 , of the valve plate with the suction vanes of the suction valve;

FIG. 5 shows a plan view, corresponding to FIG. 4 , of the valve platewithout suction vanes;

FIG. 6 shows a plan view similar to FIG. 5 , in the case of a secondexemplary embodiment of the valve plate;

FIG. 7 shows a plan view similar to FIG. 5 , in the case of a thirdexemplary embodiment of the valve plate;

FIG. 8 shows a cross section through a second exemplary embodiment of acylinder head of a piston compressor according to the invention; and

FIG. 9 shows a cross section through a third exemplary embodiment of acylinder head of a piston compressor according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

A refrigeration unit that is designated 10 as a whole comprises athermally insulated housing 12 that encloses an interior 14 in whichtemperature-sensitive goods 16 or temperature-sensitive freight 16 canbe stored, wherein the temperature-sensitive goods 16 ortemperature-sensitive freight 16 is surrounded by a gaseous medium 18,in particular air, which is kept at a defined temperature level in orderto keep the temperature-sensitive freight 16 or temperature-sensitivegoods 16 within a particular temperature range.

The refrigeration unit 10 preferably takes the form of a transportablerefrigeration unit, for example as a superstructure for a truck or afreight car or as a conventional transport container for transportingtemperature-sensitive freight 16, either by truck or by rail or sea.

So that a defined or predetermined temperature range for the freight 16can be maintained, a circulation stream 22 of the gaseous medium 18 runswithin the interior 14, wherein, starting from a temperature-controlunit 24, an incoming stream 26 enters the interior 14, flows throughthis and enters the temperature-control unit 24 again as an outgoingstream 28.

In this context, the circulation stream 22 is generated by a fan unit 32that is arranged in the temperature-control unit 24 and is kept at thedesired temperature by an internal heat exchanger 34 arranged in thetemperature-control unit 24.

Preferably here, the incoming stream 26 exits from thetemperature-control unit 24 in a region close to a top wall 36 of theinsulated housing 12, and the circulation stream 22 is preferablyreturned to the temperature-control unit 24 close to a bottom wall 38 ofthe insulated housing 12 and in so doing forms the outgoing stream 28that flows back to the temperature-control unit 24.

In particular, the temperature-control unit 24 is arranged close to thetop wall 36 of the insulated housing 12, and for example close to afront wall 48 or close to a back wall 48 thereof.

An assembly unit 52 comprising a refrigerant compressor unit 54 with arefrigerant compressor 56 and an electric drive motor 58 is arranged onthe thermally insulated housing 12, preferably close to thetemperature-control unit 24, wherein the assembly unit 52 preferablyadditionally comprises a first external heat exchanger 62 and anexternal fan unit 64 that generates for example an air stream 66 fromambient air, which passes through the first external heat exchanger 62.

As illustrated in FIG. 2 , the refrigerant compressor unit 54, theinternal heat exchanger 34 and the first external heat exchanger 62 arearranged in a refrigeration circuit, designated 70 as a whole, of arefrigeration plant 60 that is integrated into the refrigeration unit.

The refrigeration circuit 70 is connected to a high-pressure connector72 of the refrigerant compressor unit 54, in particular taking the formof a reciprocating piston compressor, from which a supply conduit 74leads to the first external heat exchanger 62, which cools an overallmass flow G of refrigerant, in the present case in particular CO₂, thathas been compressed to high pressure PH by the refrigerant compressor54, wherein in the case of CO₂ the refrigerant is in a transcriticalstate.

Here, in the first external heat exchanger unit 62 on the high-pressureside, the refrigerant may be cooled either by ambient air or indeed alsoby contact with a heat-absorbing medium of any kind, for example alsocooling water.

Downstream of the external heat exchanger 62, the overall mass flow Gthat is supplied at the high-pressure connector 72 of the refrigerantcompressor unit 54 in the refrigeration circuit 70 flows, in the case ofCO₂ in a transcritical state, through an expansion member 76 that isarranged in the refrigeration circuit 70 is expanded by this to anintermediate pressure PZ and then enters an intermediate-pressurecollector 82 in which the overall mass flow G, cooled as a result ofexpansion, is divided into a main mass flow H comprising liquidrefrigerant, which is deposited in the intermediate-pressure collector82 as a liquid refrigerant bath 84, and an additional mass flow Z, whichforms a gas bubble 86 above the liquid bath 84.

The main mass flow H comprising liquid refrigerant is supplied from theintermediate-pressure collector 82 to a cooling stage 92, which has acooling expansion member 94 that cools the main mass flow H as a resultof expansion to low pressure PN, and from which the main mass flow Henters the internal heat exchanger 34 on the low-pressure side, in whichit is able to take heat from the circulation stream 22 in the interior18 of the refrigeration unit 10 as a result of making refrigerationcapacity available.

The main mass flow H that is heated in the heat exchanger 34 then entersthe refrigerant compressor unit 54 at low pressure PN, by way of alow-pressure connector 102.

As illustrated in FIG. 2 , the refrigerant compressor 56 of therefrigerant compressor unit 54 takes the form of a reciprocating pistoncompressor, and preferably comprises a first compressor stage 112,formed by two cylinder units 114 a and 114 b which are respectivelydriven by a cylinder drive 115 a, 115 b, in particular an eccentricdrive, and of which each draws in the refrigerant of the main mass flowH by suction from a suction chamber 116 a, 116 b and discharges it forexample to a common outlet chamber 118. During this, the firstcompressor stage 112 compresses the refrigerant from the main mass flowH that is supplied thereto at low pressure, for example at values offrom 0.1 bar to 60 bar, to a medium pressure PM, of which for examplethe values lie in the range of from 20 bar to 120 bar.

Then, the main mass flow H that has been compressed to medium pressurePM is supplied from a medium-pressure outlet 122 of the common outletchamber 118 to a second external heat exchanger 124 on themedium-pressure side, which is for example likewise arranged in theassembly unit 52 and through which for example the external air stream66 likewise flows.

As a result of the second external heat exchanger 124 on themedium-pressure side, it is possible to cool the refrigerant of the mainmass flow H that has been compressed to medium pressure PM back to atemperature close to ambient temperature, and to take from it again asubstantial proportion of the heat supplied during compression.

From the second external heat exchanger 124 on the medium-pressure side,the refrigerant of the main mass flow H that has been cooled andcompressed to medium pressure PM is supplied by way of a medium-pressuresupply conduit 126 to a medium-pressure inlet 128 of an overall housing130 of the refrigerant compressor unit 54, wherein the medium-pressureinlet 128 is arranged in particular in a motor housing 132 of theoverall housing 130 of the refrigerant compressor unit 54.

Moreover, the medium-pressure supply conduit 126 is also connected tothe gas bubble 86 of the intermediate-pressure collector 82, with theresult that the additional mass flow Z is likewise supplied to themedium-pressure connector 128 of the refrigerant compressor unit 54 fromthe intermediate-pressure collector 82 by way of the medium-pressuresupply conduit 126, and the medium pressure PM is for example set tocorrespond to the intermediate pressure PZ.

The medium-pressure inlet 128 is preferably arranged in the motorhousing 132 such that the incoming refrigerant enters a motorcompartment 134, passes through the motor compartment 134 in a mannercooling the electric drive motor 58, in particular cooling a rotor 136and a stator 138 thereof, and then, guided through the overall housing130, enters a second compressor stage 142 of the refrigerant compressorunit 54.

The second compressor stage 142 likewise comprises two cylinder units144 a and 144 b which are respectively driven by a cylinder drive 145 a,145 b, in particular an eccentric drive, wherein the refrigerant thathas been compressed to medium pressure PM and supplied to the secondcompressor stage 142 enters the cylinder units 144 a and 144 b forexample by way of inlet chambers 146 a and 146 b, is compressed in thesecylinder units 144 a and 144 b and then exits to an outlet chamber 148that is connected to the high-pressure connector 72.

In the first exemplary embodiment of the reciprocating piston compressor54 according to the invention, the cylinder units 114 a and 114 b of thefirst compressor stage 112 and the cylinder units 144 a and 144 b of thesecond compressor stage 142 are driven by way of a common drive shaft152, in particular an eccentric shaft, which acts on the respectivecylinder drives 115 a, 115 b and 145 a, 145 b and is preferablyconnected coaxially and in particular in one piece with a rotor shaft154 of the rotor 136, and forms an overall drive shaft 188 therewith.

Further, in the first exemplary embodiment of the refrigerant compressorunit 54, the cylinder drive compartment 156, which receives the driveshaft 152 and the cylinder drives 115 a, 115 b, 145 a, 145 b and adjoinseach of the cylinder units 114 a and 114 b or 144 a and 144 b, isconnected within the overall housing 130 to the motor compartment 134 ormerges into this, with the result that the cylinder drive compartment156 is at medium pressure.

This has the advantage that as a result, in particular in the case ofthe second compressor stage 142, only pressure differences betweenmedium pressure and high pressure occur in the cylinder units 144 a and144 b, and thus the load on the cylinder drives 145 a and 145 b for thecylinder units 144 a, 144 b is smaller than if there were low pressurein the cylinder drive compartment 156.

Similarly, the load on the cylinder units 144 a and 144 b themselves, inparticular the pistons thereof, is also smaller than if there were lowpressure in the cylinder drive compartment 156.

As illustrated in FIG. 2 , in the first exemplary embodiment of therefrigerant compressor unit 54 according to the invention, it takes theform of a semi-hermetic compressor, in which the refrigerant compressor56 and the electric drive motor 58 are arranged in the overall housing130, which comprises a housing sleeve 162, bearing covers 164 and 166that are arranged on either side of the housing sleeve 162, and bearingreceptacles 174 and 176 that are integrally formed on the bearing covers164 and 166 and are made for example from aluminum, wherein arranged inthe bearing receptacles 174 and 176 are roller bearings 184 and 186,which in this case form the mounting for an overall drive shaft 188comprising the drive shaft 152 and the rotor shaft 154.

Further, respectively arranged on the housing sleeve 162 are cylinderheads 192 and 194, which are likewise made for example from aluminum,wherein the cylinder head 192 is associated with the cylinder units 114a and 114 b and has the low-pressure connector 102 that is connected tothe inlet chambers 116 a and 116 b, and has the outlet chamber 118 thatis connected to the medium-pressure outlet 122.

The cylinder head 194 is associated with the cylinder units 144 a and144 b, wherein the inlet chambers 146 a and 146 b are connected to themotor compartment 134 and/or the cylinder drive compartment 156, and theoutlet chamber 148 is connected to the high-pressure connector 72.

For the purpose of controlling the electric drive motor 58, there isprovided in particular a converter 212, which is preferably likewisearranged in the assembly unit 52.

With this converter, the electric drive motor 58 is operable with speedcontrol, and thus the refrigeration capacity of the refrigerantcompressor unit 54 is also continuously variably controllable within aprovided capacity range.

As illustrated in FIG. 3 , each of the cylinder units 114 has a cylinder224, which is provided in a cylinder block 222, for example formed bythe overall housing 130, and in which a piston 226 is movable, whereinthe piston delimits a cylinder chamber 228 lying between the piston 226and a valve plate 232 that closes off the respective cylinder 224,wherein the valve plate is sealed off in relation to the cylinder block222, for example by way of a gasket 234.

For the purpose of drawing the refrigerant in by suction, the valveplate 232 is provided with a suction valve 240 that a suction opening242 a having a suction vane 246 a associated therewith and moreover anoutlet valve 243 with an outlet opening 244 and an outlet vane (notillustrated).

In this case, the suction opening 242 is configured to be sealed off bythe suction vane 246, which is arranged on the valve plate 232 on a sidefacing the cylinder chamber 228 and, in the region of a suction vanefoot 252, is fixedly connected to the valve plate 232 and then extendsfrom the suction vane foot 252 beyond the suction opening 242 as far asa suction vane end 254 a, and in so doing, in its position that closesthe suction opening 242 and is illustrated in FIG. 3 , extends beyondthe suction opening 242 and abuts against an abutment face 256 a of thevalve plate 232 for the purpose of sealing off the suction opening 242.

In the simplest case, the abutment face 256 here is formed by asubregion of the side 258 of the valve plate that faces the cylinderchamber 228 and engages over the cylinder chamber 228.

In this case, the abutment face 256 is delimited on the side 258 of thevalve plate 232 by an external contour of the respective suction vane246, and by the suction opening 242.

In the exemplary embodiment illustrated in FIG. 4 , two suction vanes246 a and 246 b are provided, which serve to close two suction openings242 a and 242 b that lead into the cylinder chamber 228, wherein forexample the two suction vane feet 252 a and 252 b are additionallyconnected to one another, while the suction vane ends 254 a and 254 bare movable in relation to one another.

Moreover, for each of the suction vanes 254 a and 254 b, the suctionvane end 254 a, b, as illustrated for example in FIG. 3 in the contextof the suction vane end 254 a, is arranged in a recess 264 that forms anabutment face 266 in order to limit movement of the respective suctionvane, in this case the suction vane 246 a, as it uncovers the respectivesuction opening, for example the suction opening 242 a.

As illustrated in FIG. 4 , two suction openings 242 a and 242 b areprovided for the respective cylinder 224 in order to make available thelargest possible inflow cross section.

Moreover, for example three outlet openings 244 are provided in orderalso to make available an optimal outlet cross section for thepressurized refrigerant.

As illustrated in FIG. 4 , moreover the spatial conditions for providinga sufficient cross section for the suction openings 242 and the outletopenings 244, all of which have to lie inside the external contour ofthe respective cylinder chamber 228, are limited.

Furthermore, as is also clear from FIG. 4 , the spatial possibilitiesfor making the suction openings 242 larger are also limited by the factthat there is provided in the respective cylinder head, for example thecylinder head 192, a separating wall 272 for separating for example thesuction chamber 116 a from the outlet chamber 118, and this separatingwall 272 necessarily extends as far as the valve plate 232 and is sealedin relation to the valve plate 232 by a gasket 274 for sealing off theentire cylinder head 192.

In order to increase the efficiency of the reciprocating pistoncompressor, in particular by opening the respective suction vane 246 asquickly as possible as the drawing in of refrigerant by suction throughthe respective suction opening 242 begins, in a first embodiment thereis provided a recess 282, for example the recess 282 a or the recess 282b in FIG. 4 , adjoining the respective suction opening 242, and theselie inside the respective external contour 262 of the correspondingsuction vane 246 a, b and extend from the respective abutment face 256 aand 256 b of the respective suction vane 246 a and 246 b as far as arecess base 284 that runs opposite the corresponding abutment face 256 aand 256 b in the valve plate 232, at a depth that is greater than thethickness of a lubricant film that is formed by the lubricant in thereciprocating piston compressor, such that when the suction vane 246 a,b is closed the respective recess 282 a, b cannot be closed, entirely orin part, by a lubricant film, but rather when the suction vane 246 a, bis closed the lubricant under suction pressure flows into the recess 282from the respective suction opening 242, and thus, at the negativepressure prevailing in the cylinder chamber 228, the respective suctionvane 246 a, b is acted on by suction pressure over a larger surface areathan would be the case if the suction vane 246 a, b were only acted onin the region of the suction opening 242.

Preferably in this case, in the abutment face 256 a, b of the respectivesuction vane 246 a, b the recess 282 a, b has an external contour 286that surrounds at least 20% of a cross-sectional surface area of thesuction opening 242 a, b, such that as a result the force on therespective suction vane 246 a, b is significantly increased as it islifted away from the respective abutment face 256 a, b, and thus openingof the suction vane 246 a, b can be performed more quickly during theprocedure of drawing in by suction.

In order to achieve secure sealing between the respective suction vane246 a, 246 b and the abutment face 256 a, 256 b, it is preferablyprovided for the respective suction opening 242 a, 242 b and theassociated recess 282 a, 282 b to be together surrounded by a contactface 288 a and 288 b that runs peripherally all the way around them andis part of the abutment face 256 a, 256 b, and thus, when the suctionopening 242 a or 242 b is closed by the respective suction vane 246 aand 246 b respectively, ensures proper and reliable sealing between therespective suction vane 246 a and 246 b and the corresponding abutmentface 256 a and 256 b, and moreover also ensures that the respectivesuction vane 246 a or 246 b has a sufficiently large flat contactsurface area 256 a and 256 b to avoid damage to the respective suctionvane 246 a or 246 b.

In the exemplary embodiment of the valve plate 232 that is illustratedin FIGS. 4 and 5 , the respective recess 282 a and 282 b extends in thedirection of the respective suction vane foot 252 a, b, in particular—asdescribed—over the region of the side 258 of the valve plate 232 facingthe cylinder chamber 228, against the opposite side of which theseparating wall 272 of the cylinder head 192 is supported.

As an alternative to the form taken by the recesses 282 a, 282 b in thefirst exemplary embodiment, in a second exemplary embodiment, which isillustrated in FIG. 6 , there is the possibility of providing recesses292 a and 294 a and 292 b and 294 b, wherein the recesses 292 a and 292b extend, in the same manner as the recesses 282 a and 282 b, in thedirection of the respective suction vane foot 252 a and 252 b, while therecesses 294 a and 294 b extend from the respective suction opening 242a and 242 b in the direction of the respective suction vane end 254 aand 254 b.

Thus, an enlargement of the surface area by means of which therefrigerant that is to be drawn in by suction acts on the respectivesuction vane 246 a and 246 b to move it away from the correspondingabutment face 256 a, 256 b is is achievable on either side of therespective suction opening 242 a and 242 b.

In a third exemplary embodiment, illustrated in FIG. 7 , starting fromthe suction openings 242 a and 242 b there are provided recesses 296 aand 296 b that extend from the respective suction opening 242 a and 242b over a distance in the direction of the respective suction vane foot252 a and 252 b that is greater than a diameter of the respectivesuction opening 242 a and 242 b, for example even having an extent inthe direction of the respective suction vane foot 252 a and 252 b thatis greater than twice a diameter of the suction opening, wherein therecesses 296 a and 296 b each lie within the abutment face 256 and aremoreover likewise surrounded by a respective contact face 288 a and 288b that runs peripherally all the way around them in order to achieve asufficiently large sealing surface area to seal off the suction opening242 a and 242 b and the recess 296 a and 296 b in relation to thecylinder chamber 228.

In particular, in this solution the recesses 296 a and 296 b extend intoa region of the side 258 of the valve plate 232 facing the cylinderchamber 228, on the opposite side of which lies the outlet chamber 118in the cylinder head 196.

In a modification of the cylinder head of the first exemplaryembodiment, illustrated in FIG. 8 , the cylinder head 192′ is modifiedsuch that instead of the inlet chambers 116 a and 116 b there isprovided a suction duct 302, which extends from an outer suction end 304provided on the cylinder head 192 to the suction opening 242 as directlyas possible, with the result that a low-turbulence, if notturbulence-free flow guidance that promotes advantageous low-turbulence,preferably turbulence-free flow of the refrigerant from the outerconnector 304 to the suction opening 242 is produced for the refrigerantthat is to be drawn in by suction from the outer suction connector 304to the respective suction opening 242, and heating thereof in thecylinder head 192 is reduced.

In this exemplary embodiment, the suction duct 302 is for example shapedwithin the cylinder head 192′.

Preferably, the inlet duct 302 has a cross-sectional surface area offlow that corresponds at least to a cross-sectional surface area of flowof the respective suction opening 242 and is at most twice, even morepreferably 1.5 times, the cross-sectional surface area of flow of thesuction opening 242.

In a third exemplary embodiment of a refrigerant compressor according tothe invention, illustrated in FIG. 9 , there is provided on the cylinderhead 192″ an outer connector 306 from which two suction ducts 312 and314 branch off, each of which leads to a suction opening 242 fordifferent cylinders 224.

In this exemplary embodiment, the suction ducts 312 and 314 are forexample at least substantially shaped within an insert 316 that isinserted into the cylinder head 192″.

Here, it is preferably provided for a cross-sectional surface area offlow of the outer connector 306 to correspond at least to thecross-sectional surface area of flow into the suction ducts 312 and 314,in order to achieve flow through the cylinder head 192″ that is as lowin turbulence as possible, preferably being turbulence-free, with aslittle heating as possible of the refrigerant that is drawn in bysuction.

Preferably, the cross-sectional surface area of flow of the outerconnector 306 is at most twice, even more preferably at most 1.5 times,the sum of the cross-sectional surface areas of flow of the suctionducts 312, 314.

All the features that are described in conjunction with the cylinderhead 192 and the valve plate 232 cooperating therewith are likewiseapplicable in the cylinder head 194 and the valve plate 232 connectedthereto.

1. A reciprocating piston compressor for refrigerant, comprising a compressor housing having at least one compressor stage that has at least one cylinder unit, which itself comprises at least one cylinder chamber, wherein a piston is movably arranged in the cylinder unit, a cylinder drive that is arranged in the compressor housing, for the at least one piston, a valve plate that closes off the cylinder chamber and is provided with at least one suction valve which, for its part, has a suction opening, arranged in the valve plate and closable by a suction vane, and has at least one outlet valve with an outlet opening, wherein the at least one suction valve and the at least one outlet valve are associated with the respective cylinder chamber, and a cylinder head that is arranged on an opposite side of the valve plate to the cylinder chamber, the valve plate has, on its side facing the cylinder chamber, a recess, which is arranged inside an external contour (262) of an abutment face (256) of the suction vane (246) that is associated with the suction opening (242) and which extends from the suction opening (242) and is open toward this abutment face (256).
 2. The reciprocating piston compressor as claimed in claim 1, wherein the recess has a recess base that is set back in relation to the abutment face of the suction vane.
 3. The reciprocating piston compressor as claimed in claim 2, wherein the recess base extends into the suction opening.
 4. The reciprocating piston compressor as claimed in claim 1, wherein the recess, starting from the abutment face of the suction vane, has a depth that is greater than a thickness of a lubricant film that is formed between the suction vane and the abutment face when the suction opening is sealed off.
 5. The reciprocating piston compressor as claimed in claim 1, wherein, starting from the abutment face of the suction vane, the depth of the recess is at least 0.2 mm, in particular at least 0.3 mm.
 6. The reciprocating piston compressor as claimed in claim 1, wherein, starting from the abutment face of the suction vane, the depth of the recess is at most 40%, in particular at most 50%, of the thickness of the valve plate.
 7. The reciprocating piston compressor as claimed in claim 1, wherein the recess runs at a spacing from the external contour of the abutment face of the suction vane.
 8. The reciprocating piston compressor as claimed in claim 1, wherein the recess and the suction opening are surrounded by a contact face for the suction vane that runs peripherally all the way around them.
 9. The reciprocating piston compressor as claimed in claim 1, wherein, on its side facing the suction vane and open toward the abutment face of the suction vane, the recess has a surface area that is at least 10%, preferably at least 20%, even more preferably at least 50% of a cross-sectional surface area of the suction opening.
 10. The reciprocating piston compressor as claimed in claim 1, wherein the recess extends from the suction opening in the direction of a suction vane foot.
 11. The reciprocating piston compressor as claimed in claim 1, wherein the recess extends from the suction opening in the direction of a suction vane end.
 12. The reciprocating piston compressor as claimed in claim 1, wherein the recess extends from the suction opening over a region of the valve plate that, on the side with the cylinder head, abuts against a foot region of the cylinder head.
 13. The reciprocating piston compressor as claimed in claim 1, wherein the recess extends from the suction opening over a region of the valve plate that delimits an outlet chamber on the side with the cylinder head.
 14. The reciprocating piston compressor as claimed in claim 1, wherein the cylinder head is provided with a connector for refrigerant that is to be drawn in.
 15. The reciprocating piston compressor as claimed in claim 14, wherein a suction duct extends through the cylinder head from the connector for the refrigerant that is to be compressed as far as the suction opening.
 16. The reciprocating piston compressor as claimed in claim 15, wherein the suction duct has a duct cross section that corresponds to at most twice, even more preferably at most 1.5 times, a cross-sectional surface area of flow of the suction opening.
 17. The reciprocating piston compressor as claimed in claim 14, wherein a suction duct that leads to a plurality of suction openings has a cross-sectional surface area of flow that corresponds to at most twice, even more preferably at most 1.5 times, the sum of the cross-sectional surface areas of flow of the suction ducts.
 18. The reciprocating piston compressor as claimed in claim 15, wherein the suction duct is shaped within the cylinder head.
 19. The reciprocating piston compressor as claimed in claim 15, wherein the suction duct is formed substantially in an insert that is inserted into the cylinder head.
 20. A valve plate for a reciprocating piston compressor comprising a compressor housing having at least one compressor stage that has at least one cylinder unit, which itself comprises at least one cylinder chamber, wherein the valve plate closes off the cylinder chamber and carries a cylinder head and is provided with at least one suction valve which, for its part, has a suction opening, arranged in the valve plate and closable by a suction vane, and is provided with at least one outlet valve with an outlet opening, wherein the at least one suction valve and the at least one outlet valve are associated with the respective cylinder chamber, the valve plate has, on its side facing the cylinder chamber, a recess, which is arranged inside an external contour of an abutment face of the suction vane that is associated with the suction opening and which extends from the suction opening and is open toward this abutment face.
 21. The valve plate as claimed in claim 20, wherein the recess has a recess base that is set back in relation to the abutment face of the suction vane.
 22. The valve plate as claimed in claim 21, wherein the recess base extends into the suction opening.
 23. The valve plate as claimed in claim 20, wherein the recess, starting from the abutment face of the suction vane, has a depth that is greater than a thickness of a lubricant film that is formed between the suction vane and the abutment face when the suction opening is sealed off.
 24. The valve plate as claimed in claim 20, wherein, starting from the abutment face of the suction vane, the depth of the recess is at least 0.2 mm, in particular at least 0.3 mm.
 25. The valve plate as claimed in claim 20, wherein, starting from the abutment face of the suction vane, the depth of the recess is at most 40%, in particular at most 50%, of the thickness of the valve plate.
 26. The valve plate as claimed in claim 20, wherein the recess runs at a spacing from the external contour of the abutment face of the suction vane.
 27. The valve plate as claimed in claim 20, wherein the recess and the suction opening are surrounded by a contact face for the suction vane that runs peripherally all the way around them.
 28. The valve plate as claimed in claim 20, wherein, on its side facing the suction vane and open toward the abutment face of the suction vane, the recess has a surface area that is at least 10%, preferably at least 20%, even more preferably at least 50% of a cross-sectional surface area of the suction opening.
 29. The valve plate as claimed in claim 20, wherein the recess extends from the suction opening in the direction of a suction vane foot.
 30. The valve plate as claimed in claim 20, wherein the recess extends from the suction opening in the direction of a suction vane end.
 31. The valve plate as claimed in claim 20, wherein the recess extends from the suction opening over a region of the valve plate that, on the side with the cylinder head, abuts against a foot region of the cylinder head.
 32. The valve plate as claimed in claim 20, wherein the recess extends from the suction opening over a region of the valve plate that delimits an outlet chamber on the side with the cylinder head. 